Eversible locking mechanism for modular stents

ABSTRACT

The present invention provides an apparatus and method for locking self-expanding modular stent components together using an eversible extension on the male component. The male component is deployed partially within the female component, and with the eversible extension eversed over the male component.

TECHNICAL FIELD

[0001] This invention relates generally to luminal stents, and moreparticularly to a method and apparatus for providing a secure connectionbetween components of a modular stent.

BACKGROUND OF THE INVENTION

[0002] Modular stents are used to treat luminal defects in a human body.For example, a modular stent comprising an aortic bifurcate componentand an iliac limb component may be used to bypass an abdominal aorticaneurysm (AAA). In this exemplary modular stent, the aortic bifurcatecomponent is a bifurcated female covered stent or stent-graft (sometimesreferred to as a long leg-short leg) configured for placement in theaorta proximate the aortic bifurcation with a long leg extending intoone of the iliac arteries and a short leg or stump extending into theother iliac artery. The iliac limb component is a male covered stentconfigured for placement in the iliac artery in which the short legextends with its proximal end deployed within the short leg or stump.The stent in such combinations typically comprises an open framework ormesh of structural elements such as wires or thin metallic members,which may cross or intersect one another in various ways. In one suchstent graft configuration, a braided stent is provided where opposinghelical stent members overlap one another to form crossingintersections. Exemplary braided stents 10 are disclosed, for example,in U.S. Pat. No. 4,655,771 to Hans I. Wallsten, incorporated herein byreference. The braided stent is designed to be contracted radially forendoluminal placement into a patient and to self-expand radially into aconfiguration in which it urges the graft or covering against the wallof the body lumen in which it is disposed providing an open lumen. Usingshape memory material for the braided stent members may provide thisself-expansion. The graft in a stent-graft may be a covering or liner,disposed inside or outside of the stent and covering the stent to definea fluid passageway through the lumen of the stent.

[0003] It is important for the components of a modular stent to form asecure connection with each other to prevent relative movement of thecomponents with respect to each other due to force exerted by bloodflow, morphology of the lumen in which the modular stent is placed, orother factors. Also, with covered stents, if the connection is notsufficiently secure, these factors may cause leakage of bodily fluidbetween the modular components.

SUMMARY OF THE INVENTION

[0004] In accordance with an exemplary embodiment of the presentinvention, a modular stent system is connected by an eversible extensionon the male component of the modular stent system. An eversibleextension is formed on the male component by continued braiding of stentmembers used to form a self-expanding stent in the male component. Theeversible extension is eversed or folded back over the self-expandingstent and radially restrained in the eversed position. The eversibleextension and self-expanding stent are at least partially introducedinto a lumen of a female component of the modular stent with theeversible extension radially constrained in an eversed position. Theeversible extension and self-expanding stent are released or allowed toself-expand against the inner surface of the female component, lockingthe modular components together.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a bifurcate female component of a modular stent-graft;

[0006]FIG. 2 is a male component of a modular stent-graft with aneversible extension according to an exemplary embodiment of the presentinvention;

[0007]FIG. 3 is a cut-away view of a delivery sheath constraining themale component of FIG. 2 showing the eversible extension constrained inan eversed position by the delivery sheath;

[0008]FIG. 4 is a partial cut-away view of the delivery sheath of FIG. 3and male component of a modular stent-graft advanced into the femalecomponent of the modular stent-graft with the male component of themodular stent graft partially deployed within the female component; and

[0009]FIG. 5 shows a modular stent-graft in which the female componentand male component are connected by the eversible extension of the malecomponent according to an exemplary embodiment of the present invention.

[0010] While the applicant will describe the invention in connectionwith preferred and alternative embodiments, it should be understand thatthe invention is not limited to those embodiments. Furthermore, oneshould understand that the drawings are not necessarily to scale. Incertain instances, the applicant may have omitted details that are notnecessary for an understanding of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] The invention will next be described with reference to thefigures wherein similar numbers indicate the same elements in allfigures. Such figures are intended to be illustrative rather thanlimiting and are included herewith to facilitate the explanation of theapparatus of the present invention.

[0012] When used herein the following terms shall be understood to havethe following meanings. The term proximal shall indicate a directioncloser to a patient's heart, and the term distal shall indicate adirection farther from a patient's heart. The term stent shall indicatea generally tubular structural component for placement within a bodylumen. The terms graft and covering shall indicate a flexible tubularmember providing a passageway therethrough. The term stent-graft shallindicate a stent having a graft or covering attached thereto. Everseshall mean to roll or pivot a tubular member inside out.

[0013]FIGS. 1 and 2 show a female component 30 and a male component 20,respectively, of a modular stent-graft, according to an exemplaryembodiment of the present invention. Male component 20 is configured tobe deployed partially within female component 30 to form the modularstent-graft. Female component 30 is a bifurcated covered stent having atrunk 31 in fluid communication with a long leg 32 and a short leg 33.Trunk 31 is configured for placement in an abdominal aorta, long leg 32is configured for placement in a first iliac artery, and a short leg oriliac stub 33 is configured to extend into a second iliac artery. Malecomponent 20 is an iliac limb configured to be deployed with itsproximal end within the iliac stub 33 of the female component to form amodular stent-graft. Both, male component 20 and female component 30,comprise a self-expanding stent (not shown), preferably a braided stentwith a graft or covering 24,34 attached thereto. In an exemplaryembodiment of the invention, covering 24 is lashed or stitched to thestent of male component 20 using a filament 22. While a modularstent-graft is illustrated and described, such as is used for treatingan aneurysm, an uncovered modular stent system is contemplated withinthe scope of the present invention. An uncovered modular stent system,for example, might be used to treat stenosis. Also, while a braidedself-expanding stent is described other self-expanding stentconfigurations are contemplated within the scope of the presentinvention.

[0014] Each self-expanding stent preferably comprises intersecting stentmembers, which are preferably helical braided to form a tubular stent.An exemplary braided stent comprises a first set of stent members woundin a first helical direction and a second set of stent members wound ina second, opposite helical direction, forming a plurality ofintersections. The first and second sets of stent members may becontinuous stent members with reversing axial direction at the ends ofmale and female components. These stent members may be wire, such asnitinol or stainless steel, or may comprise polymer or any other stentmaterial known in the art. Shape memory material such as nitinol,however, is preferred.

[0015] An eversible stent extension 21 extends from the stent in themale component 20. Eversible stent extension 21 is preferably formed bycontinuation of the braided stent members forming the self-expandingstent of male component 20. Eversible stent extension 21 is configuredto be eversed or pivoted back over the self-expanding stent, and held inthis eversed position by a delivery sheath 25 (FIG. 3). Eversible stentextension 21 is next deployed within the female component 30, thedelivery sheath 25 is withdrawn, and the eversible stent extension 21 inan eversed position locks the modular stent-graft components together.The modular stent components are connected by friction between the outersurface of the male component 20 and the inner surface of the femalecomponent 30. This friction is caused by outward force exerted by theself-expanding stent of the male component and inward force exerted dueto the hoop strength of the female component and/or the wall of the bodylumen.

[0016] Eversible stent extension 21 is pivoted outwardly and back overthe male component 20, as shown in FIG. 3. Each stent member whichcontinues into the eversible stent extension is bent at acircumferential series of locations around the stent of male component20 to everse the eversible stent extension 21. To facilitate thiseversion, eversible stent extension 21 may be outwardly flared from thediameter of the stent in male component 20 to create a greater torsionalforce on the stent members. Also, eversible extension 21 is preferablyuncovered. In an exemplary embodiment of the present invention,eversible stent extension 21 is eversed by bending it back over thestent of male component 20. After eversible extension 21 is eversed, itis introduced into a delivery sheath 25 in an eversed configuration, asshown in FIG. 3, for endoluminal delivery into a body lumen.

[0017] As shown in FIG. 3, where male component 20 is a stent-graft,eversible extension 21 is preferably eversed at the end of covering 24.The end of covering 24 is preferably stitched or lashed to the stentmembers circumferentially around the stent, such as with a continuousfilament 22. The continuous filament may be knotted around intersectingstent members. The filament may be a suture or a wire, or other materialhaving sufficient flexibility for lashing and knotting and sufficientstrength to attach a graft on a stent.

[0018] Referring now to FIG. 4, delivery sheath 25 is extended intofemale component 30, with male component radially constrained within thedelivery sheath 25 and eversible stent extension 21 restrained bydelivery sheath 25 in an eversed configuration. When male component 20is at the desired location (extending into female component 30),delivery sheath 25 is axially withdrawn along male component 20. Asshown in FIG. 4, the exposed portion of male component 20 expandsoutwardly against the inner surface of female component 30. The locationof male component 20 may be determined using, for example, radiographyor the like. Delivery sheath 25 is withdrawn from male component 20until the full length of male component 20 is free from delivery sheath25, and male component is allowed to self-expand along its entirelength, with eversible stent extension 21 still eversed over covering24.

[0019]FIG. 5 shows a connected modular stent-graft according to anexemplary embodiment of the present invention. The proximal end of malecomponent 20 is placed within the iliac stub 33 of female component 30with eversible extension 21 eversed. The outward forces exerted by theself-expanding stent and by the eversible extension trying to return toa non-eversed configuration lock the male component 20 inside the femalecomponent 30.

[0020] Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

What is claimed:
 1. A locking mechanism for use in a modularself-expanding stent system having a male stent component configured tobe deployed partially within a lumen of a female stent component; saidlocking mechanism comprising an eversible stent extension extending fromsaid male stent component and deployable within said female stentcomponent in an eversed configuration to lock said male stent componentto said female stent component.
 2. The locking mechanism of claim 1further comprising a covering attached to said modular stent componentsto form a modular stent-graft.
 3. The locking mechanism of claim 2wherein said modular stent-graft is configured for deployment in anabdominal aorta, spanning the aortic bifurcation.
 4. The lockingmechanism of claim 1 wherein said eversible stent extension is outwardlyflared.
 5. The locking mechanism of claim 1 wherein said male stentcomponent comprises one or more braided filaments.
 6. The lockingmechanism of claim 5 wherein said eversible extension is formed bycontinued braiding of one or more of said braided filaments.
 7. Thelocking mechanism of claim 6 wherein a covering is lashed to said malestent to form a stent-graft and said eversible extension extends beyondsaid covering.
 8. The locking mechanism of claim 1, further comprising adelivery sheath used to temporarily hold said eversible stent extensionin said eversed configuration.
 9. A modular stent-graft systemcomprising: a self-expanding female stent-graft component having a lumentherethrough; and a self-expanding male stent-graft component having aproximal end positionable within said lumen of said female stent-graftcomponent; said proximal end having an eversible stent extensionpositionable within said female stent-graft component in an eversedconfiguration to lock said male stent-graft component into said femalestent-graft component.
 10. The modular stent-graft system of claim 9wherein said male stent graft component comprises a self-expanding stentwith a covering lashed thereon.
 11. The modular stent-graft of claim 10wherein said self-expanding stent comprises one or more braidedfilaments.
 12. The modular stent-graft of claim 11 wherein saideversible extension comprises a continuous braiding of at least one ofsaid one or more braided filaments.
 13. The modular stent-graft systemof claim 9 wherein, prior to eversing said eversible extension, saideversible extension is flared outwardly.
 14. The modular stent-graftsystem of claim 9 wherein said female stent-graft is a bifurcatedstent-graft comprising a trunk configured for placement in an abdominalaorta, an iliac leg configured for placement in a first iliac artery,and an iliac stump shorter than said iliac leg and configured forplacement in a second iliac artery and for receiving said malestent-graft.
 15. The modular stent-graft of claim 9 wherein saideversible extension is integral with a braided stent; said braided stenthaving a covering attached thereto; said eversible extension beinguncovered.
 16. A method for connecting male and female components of amodular stent-graft comprising the steps of: endoluminally delivering afemale stent-graft component into a body lumen; providing a malestent-graft component with an eversible extension; eversing saideversible extension over said male stent-graft component; radiallyrestraining said eversible extension in an eversed position;endoluminally positioning said male stent-graft component and saideversable extension partially within said female stent-graft component;and releasing said eversable extension to lock said male stent-graftcomponent into said female stent-graft component.
 17. The method ofclaim 16 wherein said eversible extension is restrained by an axiallymovable delivery sheath.
 18. The method of claim 17 wherein saideversible extension is released by axially withdrawing said deliverysheath.
 19. The method of claim 16 wherein said eversible extension isflared outwardly such that it is eversed by introducing said malestent-graft component into a delivery sheath.